Electric submersible pumping system with gas vent

ABSTRACT

A technique is provided for pumping fluids from a wellbore. An electric submersible pumping system is deployed in a wellbore on a tubing. Free gas can potentially accumulate around the electric submersible pumping system, but a gas vent is positioned to remove free gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No.11/696,315, filed Apr. 4, 2007, entitled “Electric Submersible PumpingSystem With Gas Vent” incorporated herein.

BACKGROUND

Well completions are used in a variety of well related applicationsinvolving, for example, the production of fluids. A wellbore is drilledinto a geological formation, and a completion is deployed into thewellbore by tubing or other deployment mechanisms. Generally, thewellbore is drilled through one or more formations containing desirableproduction fluids, such as hydrocarbon based fluids.

In many of these applications, electric submersible pumping systems areused to pump fluid from the wellbore to a collection location. However,the formation of free gas at the pump intake of the electric submersiblepumping system can severely degrade pumping system performance. In someenvironments, a gas lock condition can result in which the pump isunable to deliver enough pressure to keep the pumping action continuous.

When a packer is used above the electric submersible pumping system,free gas can accumulate below the packer and eventually create a gaspocket that reaches the pump intake and triggers the gas lock condition.Attempts have been made to evacuate the gas accumulated below thepacker, but these attempts have met with limited success. Withoutsufficient removal of the accumulated gas, the submersible pump of theelectric submersible pumping system can be exposed to free gas whichreduces pumping efficiency and increases the possibility of reaching thegas lock condition.

SUMMARY

In general, the present invention provides a system and method forpumping fluids from a wellbore. An electric submersible pumping systemis deployed into a wellbore on a tubing. Free gas can accumulate aroundthe electric submersible pumping system, but a gas vent is positioned toremove the free gas.

BRIEF DESCRIPTION OF THE DRAWINGS

Certain embodiments of the invention will hereafter be described withreference to the accompanying drawings, wherein like reference numeralsdenote like elements, and:

FIG. 1 is a front elevation view of a completion deployed in a wellboreand having a gas vent positioned to remove accumulated gas, according toan embodiment of the present invention;

FIG. 2 is a front elevation view similar to that of FIG. 1 but showingan example of a gas removal flow path, according to an embodiment of thepresent invention;

FIG. 3 is a front elevation view similar to that of FIG. 1 but showingan alternate gas removal flow path, according to another embodiment ofthe present invention;

FIG. 4 is a front elevation view of a completion deployed in a wellborethat illustrates another example of a gas vent, according to analternate embodiment of the present invention;

FIG. 5 is a front elevation view of a completion deployed in a wellborethat illustrates another example of a gas vent, according to analternate embodiment of the present invention;

FIG. 6 is a front elevation view similar to that of FIG. 5 but showingan example of another gas removal flow path, according to an embodimentof the present invention;

FIG. 7 is a front elevation view of a completion illustrating analternate embodiment of the present invention; and

FIG. 8 is a front elevation view similar to that of FIG. 7 but showingan example of another gas removal system, according to an embodiment ofthe present invention.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those of ordinary skill in the art that the presentinvention may be practiced without these details and that numerousvariations or modifications from the described embodiments may bepossible.

The present invention generally relates to completions that can be usedin subterranean environments to move fluids to a desired location. Thecompletions generally comprise electric submersible pumping systemsdeployed on tubing, such as production tubing or coiled tubing. Thetubing can be utilized as a flow path for fluids produced by theelectric submersible pumping system and pumped to a desired collectionlocation. The completions also generally comprise at least one packerpositioned to form a seal between the tubing and the surroundingwellbore wall which can be in the form of a wellbore casing. Inenvironments in which the well fluids have a relatively highgas-to-liquid ratio, e.g. 20% or more, the gas can interfere with thepumping efficiency of the electric submersible pumping system.Furthermore, free gas that is separated as well fluid is drawn into apump intake or that is separated by virtue of a gas separator, collectsbeneath the packer. One or more gas vents are positioned to remove theaccumulated free gas so as not to create a gas lock condition orotherwise interfere with operation of the electric submersible pumpingsystem.

Referring generally to FIG. 1, one embodiment of a completion 20deployed in a wellbore 22 is illustrated. The wellbore 22 is drilledinto a subsurface formation 24 and may be lined with a casing 26. Thecasing 26 typically is perforated to allow flow of well fluids 28between formation 24 and wellbore 22.

In the embodiment illustrated, completion 20 comprises an electricsubmersible pumping system 30 deployed on a tubing 32, such as aproduction tubing or coiled tubing. The tubing 32 extends through anisolation device 33, e.g. a packer 34, which isolates the electricsubmersible pumping system in wellbore 22. In the embodimentillustrated, packer 34 forms a seal between tubing 32 and thesurrounding wellbore, e.g. casing 26, to seal off a desired region ofwellbore 22. A power cable 36 also is routed through packer 34 forconnection with electric submersible pumping system 30 to provide powerfor operation of the submersible pumping system.

Many types of electric submersible pumping systems 30 may be utilizeddepending on the environment, wellbore depth, fluid type, and otherfactors. In the example illustrated in FIG. 1, electric submersiblepumping system 30 comprises a submersible pump 38 which may be acentrifugal style pump. Submersible pump 38 is powered by a submersiblemotor 40 supplied with electrical power via power cable 36. Submersiblemotor 40 drives submersible pump 38 through a motor protector 42, andsubmersible pump 38 draws well fluid into the electric submersiblepumping system through a pump intake 44. Pumping system 30 also maycomprise a variety of other components, such as a gas-oil separator 46and an outlet section 48 by which submersible pumping system 30 iscoupled to tubing 32.

Gas collecting beneath packer 34 is removed through a gas vent in theform of a gas inlet 50 typically positioned below packer 34 and aboveelectric submersible pumping system 30. In the embodiment illustrated,gas inlet 50 extends through the wall of tubing 32 and into a landingprofile 52. The landing profile 52 allows pumped fluids to be conveyedaround the landing profile without commingling with free gas enteringthrough gas inlet 50.

Completion 20 also may comprise a variety of other features. Forexample, one or more sliding sleeves 54 may be positioned along tubing32. In the embodiment illustrated, one sliding sleeve 54 is positionedabove packer 34 and another sliding sleeve 54 is positioned beneathpacker 34. In some applications, completion 20 also may comprisesubsurface safety valves to enable shutting down of the well in case ofemergency. For example, a subsurface safety valve 56 may be installedalong tubing 32 between electric submersible pumping system 30 andlanding profile 52 to stop, if necessary, the flow of fluid pumped bythe electric submersible pumping system into tubing 32. By way offurther example, another subsurface safety valve 58 can be installed ingas inlet 50 to stop the flow of free gas into landing profile 52, ifnecessary. This combination of subsurface safety valves allows theentire well to be shut off in case of an emergency.

Landing profile 52 enables the formation of at least two separate flowpaths within tubing 32 so that pumped fluid and free gas can beseparately produced to surface locations or other suitable locations, asillustrated in FIG. 2. In this embodiment, a second tubing 60 is landedin landing profile 52 and extends upwardly through tubing 32 to asurface location. Second tubing 60 creates a first flow path 62, locatedbetween second tubing 60 and the surrounding tubing 32, and a secondflow path 64 within the interior of second tubing 60. By way of example,second tubing 60 may be concentrically located within tubing 32.Furthermore, second tubing 60 may comprise coiled tubing or othersuitable tubing. In one embodiment, tubing 32 comprises productiontubing, and second tubing 60 comprises coiled tubing deployed along theinterior of tubing 32.

In the embodiment illustrated in FIG. 2, gas inlet 50 is coupled influid communication with second tubing 60 and second flow path 64.Accordingly, free gas that accumulates beneath packer 34 flows into gasinlet 50, through the side wall of tubing 32, through landing profile52, and into second tubing 60 for routing to the surface or othercollection location along second flow path 64. Simultaneously, fluidproduced by electric submersible pumping system 30 bypasses landingprofile 52, as indicated by arrow 66. The fluid produced by electricsubmersible pumping system 30 is produced upwardly along first flow path62 in the space between the exterior surface of second tubing 60 and theinterior surface of tubing 32.

In an alternate embodiment, the free gas is produced along first flowpath 62, and fluid pumped by electric submersible pumping system 30 isproduced along second flow path 64, as illustrated in FIG. 3. In thisalternate embodiment, landing profile 52 is configured to direct gasentering gas inlet 50 into the space between second tubing 60 andsurrounding tubing 32. Correspondingly, landing profile 52 is configuredsuch that fluid produced by pumping system 30 is produced directlythrough landing profile 52 and into second tubing 60, as indicated byarrow 68. The fluid produced by electric submersible pumping system 30travels along second flow path 64 separated from the free gas producedalong first flow path 62.

Other embodiments of gas vents, e.g. gas inlets, can be utilized toremove free gas accumulated beneath packer 34. As illustrated in FIG. 4,for example, gas inlet 50 is connected directly into a primary flow path70 along the interior of tubing 32. A check valve 71 blocks anydischarge of pumped fluid into the annulus surrounding tubing 32 whileenabling the flow of free gas from below packer 34 and into tubing 32.The free gas and pumped fluid are commingled for production to a surfacelocation or other collection location. In this embodiment, gas inlet 50and check valve 71 may be formed as part of a tubing joint 72 positionedin production tubing 32. A subsurface safety valve 73 may be positionedabove packer 34. This style of completion is amenable to, for example,shallow packer applications.

Another alternate embodiment is illustrated in FIG. 5. In thisembodiment, packer 34 comprises at least three separate pass-throughpassages 74, 76 and 78. Pass-through passage 74 accommodates the passageof tubing 32 therethrough, and pass-through passage 76 accommodates thepassage of power cable 36 therethrough. Pass-through passage 78,however, is designed to receive a gas vent valve 80 positioned to ventfree gas from a position of accumulation beneath packer 34 to an annulusregion 82 above packer 34. Once above packer 34, the free gas can flowto the surface. An individual gas vent valve 80 or a plurality of gasvent valves 80 can be used to facilitate removal of the pocket of gasthat potentially accumulates beneath packer 34.

As illustrated in FIG. 6, the one or more gas vent valves 80 can becoupled to one or more gas vent tubes 84. The gas vent tube 84 providesa specific flow path for containing the produced free gas and directingit to a desired location, e.g. a surface location. In the embodimentillustrated, gas vent tube 84 is positioned along the annulus betweentubing 32 and the surrounding casing 26.

Another embodiment of completion system 20 is illustrated in FIG. 7.

In this embodiment, isolation device 33 comprises a pod assembly 86 thatisolates electric submersible pumping system 30 in wellbore 22. A tubing88 extends downwardly from the pod assembly 86 through a packer 90 to aregion of wellbore 22 beneath packer 90. The electric submersiblepumping system 30 draws fluid from this region of the wellbore and intopod assembly 86 through tubing 88.

Free gas can collect within pod assembly 86 and rise to an upper region92 of pod assembly 86, capped by a top 94. As illustrated in FIG. 7, atubing 96 can be placed in fluid communication with the upper region 92to enable the outflow of accumulated free gas. For example, tubing 96can be directed through top 94. Free gas flows upwardly through tubing96 and into gas inlet 50. Depending on the configuration of landingprofile 52, the free gas can be directed along either first flow path 62or second flow path 64. In this example, a subsurface safety valve 98 isdeployed in tubing 32 between landing profile 52 and pod assembly 86.Another subsurface safety valve 100 may be positioned in tubing 96.

An alternate embodiment utilizing pod assembly 86 is illustrated in FIG.8. In this embodiment, landing profile 52 and gas inlet 50 arepositioned within pod assembly 86 below top 94 in upper region 92.Again, the free gas can be directed along first flow path 62 or secondflow path 64 depending on the design of landing profile 52. The fluidpumped by electric submersible pumping system 30 is directed along theother of the first and second flow paths. In the embodiment illustratedin FIG. 8, for example, fluid pumped by electric submersible pumpingsystem 30 is directed along first flow path 62, as indicated by arrow102.

The embodiments described above provide examples of completion systemsthat utilize an electric submersible pumping system in combination witha gas vent to remove free gas from a specific collection area. The gasvents are particularly useful in venting gas from beneath a packer usedto segregate a section of the wellbore. The gas vent embodimentscomprise a variety of gas inlets and other types of vents that canremove this accumulated gas before it becomes detrimental to operationof the electric submersible pumping system. It should be noted that manyadditional or alternate components can be used in constructing theelectric submersible pumping system and other aspects of the completion.Additionally, the style of the gas vent, the number of gas ventsutilized, and the location of the gas vents can vary from oneapplication to another.

Accordingly, although only a few embodiments of the present inventionhave been described in detail above, those of ordinary skill in the artwill readily appreciate that many modifications are possible withoutmaterially departing from the teachings of this invention. Suchmodifications are intended to be included within the scope of thisinvention as defined in the claims.

1. A system, comprising: a well completion having: an electricsubmersible pumping system suspended in a wellbore by a tubing throughwhich fluid is produced from the electric submersible pumping system; apower cable to provide power to the electric submersible pumping system;and a packer having at least three separate pass-through passages toaccommodate the tubing, the power cable, and a gas vent valve,respectively, wherein the gas vent valve is positioned to vent gasaccumulated beneath the packer.
 2. The system as recited in claim 1,further comprising a secondary tubing coupled to the gas vent valve andextending to a surface location externally of the tubing suspending theelectric submersible pumping system.
 3. The system as recited in claim1, wherein the gas vent valve vents gas into an annulus surrounding thetubing above the packer.
 4. The system as recited in claim 1, furthercomprising a subsurface safety valve positioned in the tubing below thepacker.
 5. A system, comprising: a well completion having: an electricsubmersible pumping system suspended in a wellbore by a tubing throughwhich a fluid is produced by the electric submersible pumping system; apacker through which the tubing extends; and a gas inlet extendingthrough a side wall of the tubing between the packer and the electricsubmersible pumping system, the gas inlet comprising a check valve thatallows a gas accumulated beneath the packer to flow into the tubing forproduction with the fluid.
 6. The system as recited in claim 5, furthercomprising a subsurface safety valve positioned in the tubing above thepacker.
 7. The system as recited in claim 5, wherein the fluid and thegas are produced through the tubing to a surface location.
 8. The systemas recited in claim 5, wherein the tubing comprises production tubing,and the gas inlet and the check valve are formed in a tubing joint.